1. Field of the Invention
The present invention relates generally to an aid for alleviating asthmatic attacks.
2. Description of the Prior Art
People having asthma who exercise generally incur the clinical signs and symptoms of an acute asthmatic attack. In the laboratory exercise testing is frequently used to study this exercise-induced asthma.
The nature of exercise-induced asthma is not clear. Various researchers have suggested numerous mechanisms for causing asthmatic attacks following exercise. One suggested mechanism is the stimulation of the airway receptors that trigger a vagal reflex.
Stanescu, D. C., and D. B. Techulescu. 1970. Exercise- and cough-induced asthma. Respiration. 27:377-383. PA1 Simonsson, B. G., B. E. Skoogh, and B. Ekstrom-Jodal. 1972. Exercise-induced airways constriction. Thorax. 27:169-180. PA1 Kiviloog, J. 1973. Bronchial reactivity to exercise and metacholine in bronchial asthma. Scan. J. Respir. Dis. 54:347-358. PA1 Crompton, G. K. 1968. An unusual example of exercise-induced asthma. Thorax. 23:165-167. PA1 Rebuck, A. S., and J. Read. 1968. Exercise-induced asthma. Lancet. 2:429-431. PA1 Fisher, H. K., P. Holton, R. ST. J. Buxton, and J. A. Nadel. 1970. Resistance to breathing during exercise-induced asthma attacks. Am. Rev. Respir. Dis. 101:885-896. PA1 Seaton, A., G. Davies, D. Gaziano, and R. O. Hughes. 1969. Exercise-induced asthma. Br. Med. J. 3:556-558. PA1 Katz, R. M., B. J. Whipp, E. M. Heimlich, and K. Wasserman. 1971. Exercise-induced bronchospasm, ventilation and blood gases in asthmatic children. J. Allergy. 47:148-158. PA1 Simonsson, B. G., B. E. Skoogh, and B. Ekstrom-Jodal. 1972. Exercise-induced airways constriction. Thorax. 27:169-180. PA1 McNeill, R. S., J. R. Nairn, J. S. Millan, and C. G. Ingram. 1966. Exercise-induced asthma. Q. J. Med. 35:55-67. PA1 Webb, P. 1951. Air temperatures in respiratory tracts of resting subjects in cold. J. Appl. Physiol. 4:378-382. PA1 Ingelstedt, S. 1956. Studies on the conditioning of air in the respiratory tract. Acta Otolaryngol. Suppl. 131:7-80. PA1 Green, I. D., and M. S. Nesarajah. 1968. Water vapour pressure of end-tidal air of normals and chronic bronchitis. J. Appl. Physiol. 24:229-231. PA1 Exercise-induced asthma was studied in eight asthmatics using various conditions of inspired air during exercise. The exercise consisted of walking on a treadmill for 10 minutes, with a speed and grade elevation adjusted to achieve the target heat rate of approximately 90% of predicted maximum. Pulmonary function tests were performed pre- and post-exercise to determine exercise-induced asthma. With inspired air at 23.degree. C. and 15% relative humidity (RH), the post-exercise forced expiratory volume in one second (FEV.sub.1), maximal mid-expiratory flow rate (MMEF), and specific airway conductance (SGaw) decreased to an average of 69%, 59%, and 38% of the pre-exercise baseline respectively. In contrast, the exercise-induced asthma was clearly prevented in all subjects by using inspired air at 37.degree. C. and 100% RH, when the post-exercise FEV.sub.1, MMEF, and SGaw were 99%, 100%, and 91% of the baseline respectively. Inspiration of warm, dry air or humid room air partially prevented exercise-induced asthma. The results indicate that the primary stimulus for exercise-induced asthma is the heat loss and/or water loss from the airways during exercise. (Physiologist, August, 1976)
Other researchers suggest hypocapnia.
Some researchers suggest metabolic acidosis,
While other researchers suggest ventilation and profusion abnormalities.
And finally, some investigators suggest the release of pharmacologically activate mediators.
The method and apparatus of the present invention for alleviating exercise-induced asthma attacks has not been investigated nor even suggested in the above prior art known by the inventor. The method and apparatus of the present invention concerns the airway heat and water loss during exercise. For example, room air at 23.degree. C. and 30% relative humidity (RH) contains 6.1 mg. of water per liter of air. The expired air measured at the lip is 33.degree. C. and contains 36 mg. of water per liter.
Thus, in breathing one liter of room air, a person loses approximately 30 mg. of water and 18 calories of heat. At rest with normal ventilation of 10 liters of air per minute, the water and heat losses from the respiratory tract would be equivalent to 300 mg. and 180 calories per minute respectively. During moderate exercise, these values may increase five times or more. The method and apparatus of the present invention is designed to minimize heat and water loss in the asthma sufferer's lungs.
Clear and convincing evidence of the operability and utility of the method and apparatus of the present invention appears in "Heat and Water Loss from the Airways and Exercise-Induced Asthma" by W. Y. Chen and D. J. Horton. The abstract of the above-identified paper is reproduced below:
Due to the unexpected and surprising results discovered by the inventor and reported in the abovecited reference, parts of the paper are reproduced in the specification below to demonstrate the primary novelty and usefulness this invention provides for asthma sufferers over all other prior art approaches. Based upon the method and apparatus of the present invention, substantial numbers of asthma sufferers will be able to exercise either indoors or outdoors.
The results indicate that sufferers can have asthma attacks alleviated by inspiring air between 30.degree. C. to 40.degree. C., and 30% RH to 100% RH, more specifically, exercise-induced asthma attacks are inhibited by inspiring air between 37.degree. C. and 40.degree. C. and 80% RH to 100% RH. Exercise-induced asthma attacks were clearly prevented by inspiring air between 37.degree. C. to 40.degree. C. and 100% RH.